8 Intrinsic Special Variables

8.1 $DEVICE		$IO device status.
8.2 $DIALECT		Current M dialect.
8.3 $ECODE		Latest M error code.
8.4 $ESTACK		Error stack info.
8.5 $ETRAP		Standard error handler code.
8.6 $HOROLOG		Current date and time.
8.7 $IO		Current I/O device.
8.8 $JOB		PID of current process.
8.9 $KEY		Characters terminating last `READ` command.
8.10 $PDISPLAY		Current primary MWAPI display.
8.11 $PRINCIPAL		I/O channel of terminal.
8.12 $REFERENCE		Most recent global reference.
8.13 $QUIT		Whether a `QUIT` command requires an argument in the current execution context.
8.14 $STACK		Current program execution stack level.
8.15 $STORAGE		Number of bytes available in the heap.
8.16 $SYSTEM		MDC system ID of FreeM.
8.17 $TEST		Truth value of last conditional expression or result of certain `LOCK` operations.
8.18 $TLEVEL		Current level of transaction nesting.
8.19 $WITH		Current variable prefix set by `ZWITH` command.
8.20 $X		Current horizontal screen position.
8.21 $Y		Current vertical screen position.
8.22 $ZA		Current position of file on `$IO`.
8.23 $ZB		Most recent keystroke.
8.24 $ZCONTROLC		Control-C handling flag.
8.25 $ZDATE		Current date in locale-specific representation.
8.26 $ZERROR		Last error message.
8.27 $ZHOROLOG		Date and time, including milliseconds.
8.28 $ZINRPT		State of the interrupt enable/disable flag.
8.29 $ZJOB		PID of parent process, if applicable.
8.30 $ZLOCAL		Last local variable reference.
8.31 $ZNAME		Name of current M routine.
8.32 $ZPRECISION		Digits of arithmetical precision.
8.33 $ZREFERENCE		Last gvn referenced.
8.34 $ZSYSTEM		Return value of last external command.
8.35 $ZTIME		Current time in locale-specific representation.
8.36 $ZTRAP		Entryref to be executed on error condition.
8.37 $ZUT		Microseconds since the UNIX epoch.
8.38 $ZVERSION		Version of FreeM and GNU host triplet.

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